Schedule II - Condensed Financial Information of Registrant (Statements of Cash Flows (Parent Company)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net income	$ 1,756,115	$ 1,381,359	$ 1,381,062
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and (accretion) amortization	(170,638)	(20,861)	55,872
Equity in undistributed earnings of subsidiaries	11,491	(16,743)	(145,099)
Stock incentive plans	54,381	51,000	49,411
Change in:
Other liabilities	70,851	14,462	19,878
Net cash from operating activities	3,678,368	2,929,238	2,568,604
Cash (used in) from investing activities:
Proceeds from sale of fixed maturity securities	2,310,746	1,011,195	797,948
Proceeds from maturities and prepayments of fixed maturity securities	4,890,572	3,506,903	4,891,179
Cost of purchases of fixed maturity securities	(9,368,703)	(6,664,763)	(8,036,680)
Change in loans receivable	(210,816)	(29,719)	(83,212)
Change in balances due from security brokers	107,280	(33,929)	14,337
Net cash used in investing activities	(2,184,489)	(1,961,964)	(1,891,355)
Cash used in financing activities:
Purchase of common treasury shares	(303,655)	(537,163)	(94,140)
Cash dividends to common stockholders	(531,953)	(501,456)	(235,192)
Other, net	(19,984)	(22,902)	(12,848)
Net cash used in financing activities	(852,487)	(1,062,495)	(771,992)
Net increase (decrease) in cash and cash equivalents	611,552	(86,151)	(119,497)
Cash and cash equivalents at beginning of year	1,363,195	1,449,346	1,568,843
Cash and cash equivalents at end of year	1,974,747	1,363,195	1,449,346
Parent Company
Cash flows from operating activities:
Net income	1,756,115	1,381,359	1,381,062
Adjustments to reconcile net income to net cash from operating activities:
Net investment (gains) losses	(90,284)	5,895	(1,007)
Depreciation and (accretion) amortization	(5,120)	(6,753)	4,281
Equity in undistributed earnings of subsidiaries	(749,350)	(491,501)	(1,511,478)
Tax payments received from subsidiaries	432,402	373,504	321,682
Federal income taxes provided by subsidiaries on a separate return basis	(424,456)	(253,292)	(414,660)
Stock incentive plans	54,381	51,000	49,411
Change in:
Federal income taxes	(9,346)	(15,793)	(40,746)
Equity in undistributed earnings of other investments	(10,444)	0	0
Other assets	(9,888)	(5,647)	3,163
Other liabilities	114,418	(88,954)	87,100
Accrued investment income	(1,740)	1,200	890
Net cash from operating activities	1,056,688	951,018	(120,302)
Cash (used in) from investing activities:
Proceeds from sale of fixed maturity securities	598,915	748,825	543,549
Proceeds from maturities and prepayments of fixed maturity securities	260,999	82,075	83,134
Cost of purchases of fixed maturity securities	(824,476)	(732,685)	(109,289)
Change in loans receivable	64,200	17,843	(16,249)
Investments in and advances to subsidiaries, net	(238,337)	21,605	(171,062)
Change in balances due from security brokers	(71,143)	(38)	(10,289)
Net additions to real estate, furniture & equipment	(37)	(18)	(432)
Other, net	73	290	368
Net cash used in investing activities	(209,806)	137,897	319,730
Cash used in financing activities:
Net proceeds from issuance of senior notes	0	0	(914)
Repayment and redemption of debt	0	0	(426,503)
Purchase of common treasury shares	(303,655)	(537,163)	(94,140)
Cash dividends to common stockholders	(531,953)	(501,456)	(235,192)
Other, net	(26,777)	(25,384)	(23,194)
Net cash used in financing activities	(862,385)	(1,064,003)	(779,943)
Net increase (decrease) in cash and cash equivalents	(15,503)	24,912	(580,515)
Cash and cash equivalents at beginning of year	128,434	103,522	684,037
Cash and cash equivalents at end of year	$ 112,931	$ 128,434	$ 103,522